1. Field of the Invention
The present invention relates to an electrical heating device and electrical heating method for electrically heating a material to be heated.
2. Description of Related Art
An electrical heating device that electrically heats a material to be heated by bringing a pair of electrodes into contact with the material to be heated with a predetermined distance between the electrodes and supplying an electric current flowing between the electrodes has been known (see, for example, Japanese Unexamined Patent Application Publication No. 2014-031566). This electrical heating device reduces a temperature irregularity during its electrical heating process by adjusting an electrical heating time for each area of the material to be heated according to the cross-sectional area (i.e., the cross-sectional dimension) of the material to be heated.
The present inventors have found the following problem. In the above-described electrical heating device, it is possible to reduce the temperature irregularity to some extent by adjusting the electrical heating time for areas of the material to be heated that can be predicted beforehand to have a low temperature such as areas having a large cross-sectional area and areas located at the ends of the material to be heated in the width direction. However, it is impossible to adjust the electrical heating time for areas that cannot be predicted beforehand to have a low temperature or areas that have a low temperature contrary to the advance prediction, thus causing a possibility of a temperature irregularity in the material to be heated. It should be noted that even in the case where a material to be heated is supplementarily heated by using supplemental heating means separately from the main electrical heating, if the supplemental heating is performed without knowing which areas will have a low temperature, there is a possibility that a part or the whole of the material to be heated could be excessively heated by this supplemental heating.